1. Field of the Invention
The present invention relates to a hand-shake correction module for a digital camera, and more particularly, to a hand-shake correction module for a digital camera, which reduces the influence of hand-shake when taking pictures.
2. Description of the Related Art
As digital still cameras and digital video cameras have become ubiquitous, consumers' demands for high quality photographs and moving images have increased. In particular, when a CMOS (complementary metal oxidized semiconductor) sensor is used as an image pickup device, instead of a CCD (charge coupled device), picture resolution is degraded due to hand-shake. To address this problem, a hand-shake correction module is being increasingly used in digital still cameras and video cameras.
Hand shake correction can be performed using lens shifting, image pickup shifting, or lens barrel shifting. Image pickup shifting is schematically illustrated in FIG. 1. Referring to FIG. 1, a conventional hand-shake correction system 1 includes a base plate 2, a slider 3, and an image pickup device base 4. The image pickup device base 4 is equipped with an image pickup device, (not illustrated), for example, a CCD.
The image pickup device base 4 is installed on the slider 3 and can move along a Y-axis direction with respect to the slider 3. The slider 3 is installed on the base plate 2 and can move along an X-axis direction with respect to the base plate 2. Therefore, the image pickup device can move along the X-axis and Y-axis directions with respect to the base plate 2. The slider 3 and the image pickup device base 4 are driven along the X-axis and Y-axis directions by separate driving means (not illustrated) such as motors, actuators or other devices known in the art. A spring 5 is installed between a protrusion 3a of the slider 3 and a protrusion 2a of the base plate 2. The spring 5 provides an elastic force that prevents the slider 3 and the image pickup device base 4 from separating from the base plate 2 in a Z-axis direction.
The base plate 2 included in the hand-shake correction system 1 of FIG. 1 may be installed in a barrel (not illustrated) of an optical system of a digital camera and thus, moves with the digital camera. When a user of the digital camera takes a picture and the hand of the user shakes in the X-axis or Y-axis directions, the image pickup device base 4 moves in an opposite direction of the hand-shake motion to compensate for the hand-shake. However, because of the spring 5, the conventional hand shake correction system has several disadvantages as explained below.
First, a driving means of the slider 3 provides a driving force F (FIG. 2) to the slider 3. Therefore, when the slider 3 moves to the right in the X-axis direction with respect to the base plate 2, the spring 5 applies an elastic force K in the opposite direction of the driving force F in the X-axis direction. Thus, when the spring 5 is short, the elastic force K is larger, and accordingly, the operation of the driving means is obstructed. Second, since the elastic force K varies with the moving distance of the slider 3, the load of the spring 5 applied to the driving means of the slider 3 also varies, and thus, it is difficult to achieve linear control of the driving means of the slider 3.
To address these problems, the length of the spring 5 should be sufficiently long. However, when the spring 5 is long the height of the hand-shake correction system 1 increases. In addition, in order to attach a long spring 5 between the protrusions 2a and 3a, the height h (FIG. 1) may become greater than the average height of the hand-shake correction system 1. To this end, the inner space for placing other elements in the hand-shake correction system may be limited.